Increasingly stringent statutory regulations governing permissible polluting emissions in motor vehicles in which internal combustion engines are disposed make it necessary to limit the polluting emissions to an absolute minimum during the operation of an internal combustion engine. This can be accomplished on the one hand by a reduction in the polluting emissions that are produced during the combustion of the air/fuel mixture in the respective cylinder of the internal combustion engine. On the other hand exhaust gas aftertreatment systems are employed in internal combustion engines in order to convert the polluting emissions produced during the combustion process of the air/fuel mixture in the respective cylinder into harmless substances. In spark ignition engines in particular, three-way catalytic converters are used as exhaust gas catalyzers for this purpose, for example. A precisely adjusted air/fuel ratio in the cylinders is a prerequisite in order to achieve a high degree of efficiency in the conversion of polluting emissions such as e.g. carbon monoxide, hydrocarbons and nitrogen oxides. Furthermore the mixture upstream of the exhaust gas catalytic converter must also exhibit a predefined variation, that is, for example, alternating operation of the internal combustion engine in excess air mode and air deficiency mode, in order to effect a replenishment and depletion of the oxygen store of the exhaust gas catalytic converter. When oxygen is stored, the nitrogen oxides in particular are reduced, whereas when the store is emptied the oxidation process is assisted and in addition stored oxygen molecules are prevented from deactivating subsections of the exhaust gas catalytic converter.
A particularly relevant proportion of the polluting emissions normally occurs after the internal combustion engine is started and before the exhaust gas catalytic converter has reached a state of operational readiness. Heating measures which can include, for example, an injection of secondary air are known for bringing about the operational readiness of the exhaust gas catalytic converter in the swiftest possible manner.